This invention relates to a transition module for a pneumatic sequencer, especially a pneumatic sequencer having a branched flow diagram. By way of novel industrial product, the invention is also concerned with a sequencer which makes use of a module of this type.
By sequencer is meant in this case a cybernetic system for automatically initiating successive industrial operations in a predetermined order.
It is known that a sequencer of this type as conveniently represented by a flow diagram is composed of a certain number of action modules. Taken separately, an action module is a device for receiving an order on a control input and emitting an output signal so as to initiate the operation of a given machine. In a sequencer, these modules are mounted in stages so that each module is capable of initiating the operation of a machine but also of producing action on the control input of another action module located downstream with respect to the predetermined sequential order of operations.
One of the essential conditions imposed by the operation of the sequencers is a strict sequentiality of the different operations which make up the flow diagram. To this end, it is a known practice to provide each module with at least one input which is responsive to a triggering variable which produces action as an AND conjunction with the output of the module located upstream (in the direction of the sequence) so as to control the output signal of the module considered. The triggering variable can be a signal which indicates that the machine located upstream has completed its operation. It is thus ensured that the machine located downstream will begin to operate only after completion of the operation performed by the upstream machine, which accordingly represents strict sequentiality.
Similarly, it is essential to ensure that the upstream machine cannot in any event be again put into operation before the downstream machine has completed its task. This problem is similar to the preceding and can be solved by the same known means. These means are relatively simple in the case of a sequencer having a linear flow diagram, namely in which each action module communicates only with two other modules, one module being located upstream and the other being located downstream.
The same does not apply to sequencers of the branched flow diagram type in which a plurality of upstream modules are capable of producing action in conjunction (AND or OR, for example) on one and the same downstream module or alternatively in which one and the same upstream module can produce action in disjunction (AND or OR) on a plurality of downstream modules. It is necessary in that case to provide a device which performs the logical operation aforesaid and at the same time initiates the inhibitions mentioned above in order to ensure sequentiality of operations.
To this end, it is a known practice to construct modules which will be designated as control modules and comprise the equivalent of the assembly of downstream action modules and a logical operator. Control modules of this type comprise control inputs and signal outputs for actuating the machines to be controlled. However, these modules must be capable of performing any conceivable logical function, not only the four basic functions mentioned above but also more or less complex combinations of these functions in a theoretically infinite number. In consequence, these control modules must be fabricated in accordance with customers' requirements in the case of each type of sequencer.
The aim of the present invention is to produce a single-connection module designated hereinafter as a transition module for connecting the action modules of the sequencer to each other and performing the desired logical operation while having a universal character which permits the use of the module for the purpose of performing any logical function, even a complex function, and serves at the same time to establish the necessary inhibition connections for ensuring strict sequentiality of the operations of the different stages of the sequencer.